Trial Review

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been endorsed by the ANZCTR. Before participating in a study, talk to your health care provider and refer to this information for consumers
Trial registered on ANZCTR


Registration number
ACTRN12624000628549
Ethics application status
Approved
Date submitted
17/04/2024
Date registered
14/05/2024
Date last updated
6/04/2025
Date data sharing statement initially provided
14/05/2024
Type of registration
Prospectively registered

Titles & IDs
Public title
Sex differences in skeletal muscle microvascular blood flow in healthy young adults.
Scientific title
Sex differences in skeletal muscle microvascular blood flow and other cardiovascular responses to acute maximal exercise in healthy young adults.
Secondary ID [1] 311742 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Cardiometabolic diseases 333224 0
Condition category
Condition code
Cardiovascular 329914 329914 0 0
Normal development and function of the cardiovascular system

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
This is a cross-sectional study exploring potential sex differences in cardiovascular responses to a single bout of acute maximal exercise.

Intervention: single graded exercise test on a treadmill (modified Bruce protocol), to assess cardiorespiratory fitness (VO2peak), skeletal muscle microvascular blood flow, femoral artery blood flow, and cardiac responses to acute maximal exercise. Participants will begin walking at 2.7km/h with increasing speed and/or incline every three minutes until exhaustion (see below). VO2peak is calculated from the highest 10-second rolling average of breath-by-breath respiratory gas analysis (Quark RMR Gas Analyzer, Cosmed, Italy). Maximal effort (i.e., adherence to the intervention) will be determined by one or more of the following criteria: a plateau in VO2, heart rate 90% of age-predicted maximum, rating of perceived exertion (RPE) =17, and/or respiratory exchange ratio =1.1.. Electrocardiography will be recorded throughout, with heart rate, blood pressure, and RPE recorded at the end of each 3-minute stage. The testing session will be supervised by a minimum of two first aid trained research staff at Deakin University, Burwood Campus.

Modified Bruce Protocol Stages (3mins each)
Stage 1: 2.7km/h; 0% incline
Stage 2: 2.7km/h; 5% incline
Stage 3: 2.7km/h; 10% incline
Stage 4: 4km/h; 12% incline
Stage 5: 5.5km/h; 14% incline
Stage 6: 6.8km/h; 16% incline
Stage 7: 8km/h; 18% incline
Stage 8: 8.9km/h; 20% incline
Stage 9: 9.7km/h; 22% incline


Pre-intervention testing:
- Questionnaires to collect general health and medical information, menstrual cycle/oral contraceptive use, dietary habits (24 hour diet recall), and physical activity levels (questionnaire and accelerometer worn for 7 days). Participants will be required to wear the accelerometer for all waking hours, except during water-based activities (swimming/bathing). The questionnaires are one-time assessments, each requiring less than 10 minutes to complete. .
- Fasting clinical chemistries (glucose, insulin, total cholesterol, low density lipoprotein, high density lipoprotein, triglycerides, HbA1c, and female sex hormone concentrations).
- Body composition (height, weight, and lean/fat mass by DEXA).
- Central haemodynamics (systolic and diastolic pressure, pulse pressure, augmentation index, augmentation index at 75bpm, mean arterial pressure) and arterial stiffness assessed via pulse wave analysis and pulse wave velocity.
Intervention code [1] 328199 0
Treatment: Other
Comparator / control treatment
Comparator - males
Control group
Active

Outcomes
Primary outcome [1] 337679 0
Skeletal muscle microvascular blood flow responses to acute maximal exercise (composite of microvascular flow velocity and microvascular blood volume).
Assessment method [1] 337679 0
Contrast-enhanced ultrasound imaging during intravenous infusion of a commercially available contrast agent (Definity, Lantheus Medical Imaging). An L9-3 linear array transducer interfaced to a standard ultrasound machine will be used to image the vastus lateralis (thigh muscle) in cross-section. Depth, gain, and focus will be optimised for each participant and maintained during repeated imaging sequences. A contrast agent suspension (1mL of Definity diluted into 30mL of saline solution) will be infused using a syringe pump. After 4 minutes of infusion at a rate of 42mL/hr to measure Definity concentration in the cross-sectional femoral artery, the infusion rate is increased to 200mL/hr to record real-time video captures of microvascular blood flow in the vastus lateralis. Ultrasound images will be analysed using computer software. The acoustic signal produced by the contrast agent microspheres will be measured and is directly proportional to the number of active/open capillaries and volume of blood within the microvascular system. Following a high-energy ultrasound pulse, all contrast agent microspheres within the ultrasound beam will be destroyed. The rate at which the microspheres reappear provides an indication of microvascular blood velocity. Microvascular blood flow is calculated as the product of microvascular blood volume and blood velocity.
Timepoint [1] 337679 0
Pre-exercise, immediately after exercise, and 30 minutes post-exercise.
Secondary outcome [1] 432812 0
Femoral artery blood flow responses to acute maximal exercise (composite of femoral artery diameter and blood velocity).
Assessment method [1] 432812 0
2D and Doppler ultrasound imaging. Femoral artery diameter and blood velocity will be measured using a commercial ultrasound (Epiq 7, Philips Medical System, North Ryde, NSW, Australia). Diameter (two-dimensional ultrasound) will be recorded at the peak of the QRS complex (determined via three-lead electrocardiography). Blood velocity (pulsed-wave Doppler ultrasound) will be averaged over approximately ten cardiac cycles. Femoral artery mean blood flow (mL/min) is calculated as: pr2 (cm) x mean velocity (cm/s) x 60. Probe location and ultrasound settings will be recorded for repeat measures within visits.
Timepoint [1] 432812 0
Pre-exercise, 15 minutes post-exercise, and 30 minutes post-exercise.
Secondary outcome [2] 432813 0
Cardiac index
Assessment method [2] 432813 0
Echocardiography and three-lead electrocardiography. Two-dimensional and Doppler images will be obtained from the parasternal long axis view and apical four- and five-chamber views. Cardiac output will be calculated by multiplying LV outflow tract (LVOT) area (during peak systole), velocity time integral, and heart rate, indexed to body surface area.
Timepoint [2] 432813 0
Pre-exercise, immediately after exercise, and 30 minutes post-exercise.
Secondary outcome [3] 433722 0
Blood glucose
Assessment method [3] 433722 0
Venous blood collected from an antecubital vein and immediately analysed.
Timepoint [3] 433722 0
Pre-exercise, 15 minutes post-exercise, 30 minutes post-exercise
Secondary outcome [4] 433723 0
Blood lactate
Assessment method [4] 433723 0
Venous blood collected from an antecubital vein and immediately analysed.
Timepoint [4] 433723 0
Pre-exercise, 15 minutes post-exercise, and 30 minutes post-exercise

Eligibility
Key inclusion criteria
Body mass index 18.5-30kg/m2
Minimum age
18 Years
Maximum age
45 Years
Sex
Both males and females
Can healthy volunteers participate?
Yes
Key exclusion criteria
Diagnosis of insulin resistance/diabetes or cardiovascular disease; uncontrolled hypertension (brachial blood pressure >160/100mmHg); known liver/kidney disease; current or previous cancer; physical limitations to exercise; current or past smoker (12 months); currently engaging in >300mins/week of moderate to vigorous physical activity; pregnancy/lactation; irregular menstrual cycle; use of non-monophasic oral contraceptive pill; oral contraceptive pill use for non-contraceptive purposes; females who are peri- or post-menopausal; a previous reaction to Definity contrast agent.

Study design
Purpose of the study
Prevention
Allocation to intervention
Non-randomised trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Masking / blinding
Who is / are masked / blinded?



Intervention assignment
Other design features
Phase
Not Applicable
Type of endpoint/s
Statistical methods / analysis

Recruitment
Recruitment status
Recruiting
Date of first participant enrolment
Anticipated
1/06/2024
Actual
28/03/2025
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
34
Accrual to date
0
Final
Recruitment in Australia
Recruitment state(s)
VIC

Funding & Sponsors
Funding source category [1] 316074 0
University
Name [1] 316074 0
Deakin University HDR funds
Country [1] 316074 0
Australia
Funding source category [2] 316075 0
University
Name [2] 316075 0
Deakin University Alfred Deakin Postdoctoral Research Fellowship
Country [2] 316075 0
Australia
Primary sponsor type
University
Name
Deakin University
Country
Australia
Secondary sponsor category [1] 318241 0
None
Name [1] 318241 0
Country [1] 318241 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 314893 0
Deakin University Human Research Ethics Committee (DUHREC)
Ethics committee address [1] 314893 0
Ethics committee country [1] 314893 0
Australia
Date submitted for ethics approval [1] 314893 0
05/03/2024
Approval date [1] 314893 0
13/05/2024
Ethics approval number [1] 314893 0

Summary
Brief summary
Trial website
Public notes

Contacts
Principal investigator
Name 133074 0
Dr Kimberley Way
Address 133074 0
Deakin University, 221 Burwood Highway, Burwood, VIC, 3125
Country 133074 0
Australia
Phone 133074 0
+61 3 924 68894
Email 133074 0
kim.way@deakin.edu.au
Contact person for public queries
Name 133075 0
Kimberley Way
Address 133075 0
Deakin University, 221 Burwood Highway, Burwood, VIC, 3125
Country 133075 0
Australia
Phone 133075 0
+61 3 924 68894
Email 133075 0
kim.way@deakin.edu.au
Contact person for scientific queries
Name 133076 0
Kimberley Way
Address 133076 0
Deakin University, 221 Burwood Highway, Burwood, VIC, 3125
Country 133076 0
Australia
Phone 133076 0
+61 3 924 68894
Email 133076 0
kim.way@deakin.edu.au

Data sharing statement
Will the study consider sharing individual participant data?
No
No IPD sharing reason/comment: Due to confidentiality data will not be shared.



What supporting documents are/will be available?

TypeCitationLinkEmailOther DetailsAttachment
Ethical approval    Study-related document.pdf


Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.